Wind turbine towers, especially tubular steel towers for large wind turbines, are large in diameter and weight. This may cause difficulties concerning the transportation of a tower to the wind farm and the used infrastructure.
Slip forming for construction is a method of continuously pouring concrete into a form of mould that moves up vertically, normally with the assistance of hydraulic or screw jacks. As the forming of the structure progress, the section of previously poured concrete hardens and forms a kind of support wall that is strong enough to withstand the concrete poured over the top of it. Pouring continues until the desired height of the structure is reached, allowing for a type of concrete structure that is positioned on top of a foundation and completely hollow inside. U.S. Pat. No. 4,314,798 illustrate such a slip forming system.
The slip forming process is known in the art as being used to build wind turbine towers.
The casted concrete structure may comprise solid iron or stainless steel bars or grids for reinforcement.
It is also known to use fibers as reinforcement of concrete in wind turbine towers. US2009/0307998 is one such example. The Fibre Reinforced Concrete (FRC) is a technology which can be used together with different types of fibers such as plastics, metal, glass etc. Normally chopped fibers are mixed with the concrete to enhance the tensile properties.